In optical fiber communications systems, an optical fiber simultaneously carries many different communications channels. In the use of such a system, channels are frequently added or removed at various points--typically called nodes--in the network. For example, channels are added for long distance transmission and removed at their destination. Or if one or more paths are lost or overloaded, channels must be removed from the lost or overloaded path and added to another. An optical communications system for performing these functions is described, for example, in U.S. patent application Ser. No. 08/668,196 entitled, "Optical Fiber Transmission System With an Active Optical Router for Multiplexing" filed by Miriam deBarros et al. on Jun. 21, 1996, now U.S. Pat. No. 5,721,796 which is incorporated herein by reference.
A common problem in virtually all such optical fiber communications systems is that optical signals encounter a wide variety of different paths between receiver and transmitter, including different types of fiber and components. Different circuit paths will be established to connect a given transmitter with different receivers. Different types of fiber and components may be encountered on each path. In the absence of compensation, a signal will be degraded due to chromatic dispersion. This linear distortion mechanism becomes more severe as the bit rate is increased. Accordingly there is a need for an optical fiber communications system with a data equalizer capable of adapting to changing conditions and changing optical paths.